用于高速数据采集的DMA技术

Application of DMA Technique to High Rate Data Aquisition.

提高数传速率是设计微机控制的高速数据采集系统必须解决的一个问题。DMA技术是指外设与微机主存之间数传的一种方式。在DMA方式下 ,数传过程不是由CPU控制 ,而是在专用接口芯片DMA控制器的控制下实现的 ,它适用于外设和主存之间批量数据的高速数据传输。在微机控制的动态测试系统 ,数传一个字节的时间为 31.2 5ns,若采用程序查询或中断方式实现A/D转换器与微机主存之间的数传 ,还很难在 31.2 5ns内传输一个字节的数据 ;而采用DMA方式数传 ,用压缩时序工作 ,则在大多数情况下 ,在 2个时钟时间内完成一个字节的数传 ,因此 ,DMA数传能满足一般高速数据采集的需要 ,且有硬软件设计简单。

Increasing data transmission rate is a key to designing microcomputer controlled high rate data acquisition system. DMA technology is a way of data transmission between peripheral equipment and main memory. By means of a special interface chip,the data transmission is achieved in DMA way,this is DMA controller instead of CPU. In a dynamic test system controlled by computer,the transmission of a byte takes 31.25 ns. While by way of inquiry or interruption,the transmission of a byte can hardly be achieved in 31.25 ns. If the DMA technology and the operation of compressed time series are used, the transmission of a byte can be accomplished in two clock cycles. Therefore. the DMA transmission can satisfy the requirement of ordinary high rate data aquisition,the design of the hardware and software is more simple and its use is more flexible.